Not making a AAA game doesn’t mean you need to make your game out of BSP, which given that Indies have done it without having to use BSP it’s clear that BSP isn’t necessary for indies to be successful. Not that BSP is an advantage in the first place anyways. It seems it’s only a way of working that some people prefer and not something that’s really going to improve game development.
And by the way, the team that worked on Gears of War 1 was extremely small, like 20 people I believe, being indie doesn’t mean you can’t have a complete game of high quality. And again, BSP doesn’t necessarily make it easier, because you can still do what you need to with a 3D app and it’s not going to take longer. As evidenced by the many games that do that already.